If you keep all of them in a big array then they are all indexed. Then

you can have a array of 10 (or so) integers that keeps track of the
current 10 in use. When a new sample needs playing you look up in that
array what the oldest sample is, unchuck that, replace the number with
the number of the new one and chuck the new one to dac. Then you just
need to cover for re-triggering buffers that are already connected,
but that's quite simple.

That will work, but it won't deal with clicks for you. How hard clicks
are to deal with will depend on how dense your drumming gets, compared
to the length of the sample. If you are lucky you won't need to care
at all.

Yours,
Kas.